Preserving quotes in Batch file %*

I want to forward %* to a powershell script from a Batch script, which already sort of works. The only problem is that I can't forward arguments with spaces cleanly.

Example.bat..

@echo off

set cwd=%~dp0
set argv=%*
powershell -NoProfile -ExecutionPolicy Bypass -Command "& '%cwd%Example.ps1' %argv%"

Example.ps1..

Param(
  $Message
)
If (!$Message)
{
  $Message = "Hello!!!"
}
Write-Host $Message

I can do ./Example.bat Oh just fine, which prints Oh. However, ./Example.bat "Oh no" only prints Oh as well. ./Example "'Oh no'" works but is not clean, as then the usage of the scripts isn't identical anymore, which means any use of it becomes tightly coupled, which I don't want.

Solution

Fabrice SANGA's helpful answer explains the need to escape the " chars. embedded in the value of %* well and offers a solution that will typically work, using \" escaping.

However, it isn't robust, because it breaks cmd.exe's own parsing with "..."-enclosed arguments that contain cmd.exe metacharacters such as & or |, e.g. "you & I"

^{Update: The linked answer has since been updated with an alternative solution that attempts to provide a robust solution, but the one below is simpler.}

A robust solution requires a different - obscure - form of escaping embedded " chars., namely as "^"" [sic] rather than as \"

Note: This applies to powershell.exe, the Windows PowerShell CLI; with pwsh.exe, the PowerShell (Core) 7 CLI, use ""

Here's a robust, streamlined solution that also uses this form of escaping to enclose the target *.ps1 path, so as to also handle paths with embedded ' chars. correctly.
Also note the use of %~dpn0.ps1, which obviates the need to repeat the base file name, Example:

@echo off & setlocal

:: Escape any " chars. embedded in %* as "^""
set argv=%*
if defined argv set argv=%argv:"="^""%

powershell -NoProfile -ExecutionPolicy Bypass -Command "& "^""%~dpn0.ps1"^"" %argv%"

^{setlocal is used to ensure that the variables defined in the batch file are scoped to that file; by default, they would be defined session-globally.}

^{Tip of the hat to João Mac's answer for the reminder of the if defined somevar technique as a variable emptiness/non-existence test, which is simpler than if not %somevar%.==.}

Note: More work is needed if you additionally need to guard against ` and $ chars. in the script path and / or arguments getting interpreted by PowerShell (as the escape character and as the start of a variable reference such as $HOME or a subexpression such as $(1 + 2), respectively):

@echo off & setlocal

:: Escape any " chars. embedded in %* as "^"",
:: ` as ``, and $ as `$
set argv=%*
if defined argv set argv=%argv:"="^""%
if defined argv set argv=%argv:`=``%
if defined argv set argv=%argv:$=`$%
:: Do the same to the script file path,
:: but defer enclosing the path in "^""..."^"" until later.
set "ps1path=%~dpn0.ps1"
set "ps1path=%ps1path:`=``%"
set "ps1path=%ps1path:$=`$%"

powershell -NoProfile -ExecutionPolicy Bypass -Command "& "^""%ps1path%"^"" %argv%"

However, you should then consider using the -File CLI parameter instead, which greatly simplifies the approach - see the next section.

Taking a step back:

If your intent is solely to call a *.ps1 file with arguments, it is better to use the -File (-f) CLI parameter rather than -Command (-c)

Doing so has two advantages:

It obviates the need for escaping and therefore greatly simplifies your batch file (see below).
It protects your script-file path and any arguments from potentially unwanted interpretation by PowerShell: e.g., with -File, passing verbatim $HOME as an argument is passed through as-is, whereas with -Command it would be expanded as PowerShell's automatic $HOME variable.

@echo off & setlocal

powershell -NoProfile -ExecutionPolicy Bypass -File "%~dpn0.ps1" %*

For detailed guidance on when to use -File vs. -Command, see this answer.